CT603 is a notice from HMRC to a company to file its corporation tax return. HMRC would normally send out these notices within a few weeks of the end of the period of accounts. The company is not obligated to file a return until this notice is issued.Howevever, when your company has not received a CT603, it must notify HMRC within 12 months of the accounting period that it is chargeable to corporation tax. None of these is to vbe concerned about, your accountant is nromally on top of these things.

Corporation tax payment for a small business is due nine months and 1 day after the end of the accounting period. Note that the accounting period for Corporation tax is never longer than 12 months so if your accounting period is longer than 12 months, your accountant would have prepared 2 sets of corporation tax returns for you with different due dates.

CT600 is the corporation tax return that incorporated companies (Limited and PLC) must file. It is like a self-assessment return but for a company. The CT600 must be filed online within 12 months of a company's year-end.The return must include a set of accounts and any detailed computations necessary to show the return is correct and complete. Accountants and Tax Advisors usually use a software product to help them complete this and file it online

CT600 must be submitted online to HMRC by the later of: - Twelve months from the end of the period of account (say period of account ends 31/12/23, CT600 must be filed by 31/12/2024) and - Three months from the receipt of CT603

A period of accounts is the period when a company prepares its accounts. This is technically different from an accounting period, which is the accounting period used for the calculation of corporation tax. Accounting periods cannot be longer than 12 months, while periods of accounts can be as long as 18 months as authorised in the Companies Act.